Distribution of Gaussian Process Arc Lengths

We present the first treatment of the arc length of the Gaussian Process (GP) with more than a single output dimension. GPs are commonly used for tasks such as trajectory modelling, where path length is a crucial quantity of interest. Previously, only paths in one dimension have been considered, with no theoretical consideration of higher dimensional problems. We fill the gap in the existing literature by deriving the moments of the arc length for a stationary GP with multiple output dimensions. A new method is used to derive the mean of a one-dimensional GP over a finite interval, by considering the distribution of the arc length integrand. This technique is used to derive an approximate distribution over the arc length of a vector valued GP in $\mathbb{R}^n$ by moment matching the distribution. Numerical simulations confirm our theoretical derivations.Comment: 10 pages, 4 figures, Accepted to The 20th International Conference on Artificial Intelligence and Statistics (AISTATS

Effects of a Three-day Period of Intense, Intermittent Exercise on Oxidative Stress and Inflammation

It is documented that strenuous and prolonged exercise induces oxidative stress and inflammation, with the associated muscle damage and fatigue compromising performance. Little is known about the oxidant effects of intense, intermittent exercise, as performed daily by elite athletes competing in team sports. PURPOSE: To assess the short-term effects of a 3-day period of intense, intermittent exercise on biomarkers of oxidative stress and inflammation in trained athletes. METHODS: Ten trained athletes (age: 32.11±1.91yrs; mass: 66.33±1.95kg; maximal oxygen uptake (VO2max): 51.44±1.59mL·kg·minˉ1) completed a high-intensity, intermittent exercise protocol (90-minute intermittent treadmill run, ~70% VO2max) on three consecutive days and were compared to a control group (N=10). Blood samples were collected immediately pre (T1) and post (T2) the 3-day exercise protocol, then 21h- (T3) and 42h-post-exercise (T4); and assayed for Total Antioxidant Status (TAS), Thiobarbituric Acid Reactive Substances (TBARS), Interleukins (IL-6, IL-8 and IL-10), C-Reactive Protein (C-RP) and Lactate Dehydrogenase (LDH). Data were corrected for plasma volume change; results presented as M±SE. RESULTS: No significant differences were observed between the exercise and control group at T1 (TAS: 1.20±0.14mmol.L-1 vs. 1.18±0.11mmol.L-1; LDH: 302.14±16.24U/L vs. 295.27±31.26U/L; TBARS: 6.21±1.09μM vs. 5.88±1.00μM; and IL-6: 0.67±0.70pg/ml vs. 1.12±0.28pg/ml). The 3-day exercise period caused a significant increase in LDH (413.24±35.27U/L, P = 0.029), IL-6 (2.54±0.35pg/ml, P = 0.037) and TBARS (7.00±0.61μM, P = 0.042) at T2, with the effects of TBARS remaining above baseline at T4 (6.43±0.79μM, P = 0.043). TAS increased post-exercise with a significant difference observed between groups at T2 (1.86±0.21mmol.L-1 vs. 1.20±0.13mmol.L-1, P = 0.006), T3 (1.86±0.28mmol.L-1 vs. 1.30±0.14mmol.L-1, P = 0.010) and T4 (1.71±0.22mmol.L-1 vs. 1.17±0.13mmol.L-1, P = 0.014). IL-8, IL-10, and C-RP did not differ between groups. CONCLUSIONS: A 3-day period of intense, intermittent exercise increased oxidative stress and upregulated antioxidants in trained athletes, confirming the current model that exercise-induced oxidants play an important role in intracellular signaling pathways of endogenous antioxidants

On the Rozansky-Witten weight systems

Ideas of Rozansky and Witten, as developed by Kapranov, show that a complex symplectic manifold X gives rise to Vassiliev weight systems. In this paper we study these weight systems by using D(X), the derived category of coherent sheaves on X. The main idea (stated here a little imprecisely) is that D(X) is the category of modules over the shifted tangent sheaf, which is a Lie algebra object in D(X); the weight systems then arise from this Lie algebra in a standard way. The other main results are a description of the symmetric algebra, universal enveloping algebra, and Duflo isomorphism in this context, and the fact that a slight modification of D(X) has the structure of a braided ribbon category, which gives another way to look at the associated invariants of links. Our original motivation for this work was to try to gain insight into the Jacobi diagram algebras used in Vassiliev theory by looking at them in a new light, but there are other potential applications, in particular to the rigorous construction of the (1+1+1)-dimensional Rozansky-Witten TQFT, and to hyperkaehler geometry

A chromatin modifying enzyme, SDG8, is involved in morphological, gene expression, and epigenetic responses to mechanical stimulation

Thigmomorphogenesis is viewed as being a response process of acclimation to short repetitive bursts of mechanical stimulation or touch. The underlying molecular mechanisms that coordinate changes in how touch signals lead to long-term morphological changes are enigmatic. Touch responsive gene expression is rapid and transient, and no transcription factor or DNA regulatory motif has been reported that could confer a genome wide mechanical stimulus. We report here on a chromatin modifying enzyme, SDG8/ASHH2, which can regulate the expression of many touch responsive genes identified in Arabidopsis. SDG8 is required for the permissive expression of touch induced genes; and the loss of function of sdg8 perturbs the maximum levels of induction on selected touch gene targets. SDG8 is required to maintain permissive H3K4 trimethylation marks surrounding the Arabidopsis touch-inducible gene TOUCH 3 (TCH3), which encodes a calmodulin-like protein (CML12). The gene neighboring was also slightly down regulated, revealing a new target for SDG8 mediated chromatin modification. Finally, sdg8 mutants show perturbed morphological response to wind-agitated mechanical stimuli, implicating an epigenetic memory-forming process in the acclimation response of thigmomorphogenesis

The effect of a decaffeinated green tea extract formula on fat oxidation, body composition and exercise performance

Background: The cardio-metabolic and antioxidant health benefits of caffeinated green tea (GT) relate to its catechin polyphenol content. Less is known about decaffeinated extracts, particularly in combination with exercise. The aim of this study was therefore to determine whether a decaffeinated green tea extract (dGTE) positively influenced fat oxidation, body composition and exercise performance in recreationally active participants. Methods: Fourteen, recreationally active males participated in a double-blind, placebo-controlled, parallel design intervention (mean±SE; age = 21.4±0.3 yrs; weight = 76.37±1.73 kg; body fat = 16.84±0.97 %, peak oxygen consumption [V̇O2peak] = 3.00±0.10 L·min-1). Participants were randomly assigned capsulated dGTE (571 mg·d-1; n=7) or placebo (PL; n=7) for 4 weeks. Following body composition and resting cardiovascular measures, participants cycled for 1 hour at 50% V̇O2peak, followed by a 40 minute performance trial at week 0, 2 and 4. Fat and carbohydrate oxidation was assessed via indirect calorimetry. Pre-post exercise blood samples were collected for determination of total fatty acids (TFA). Distance covered (km) and average power output (W) were assessed as exercise performance criteria. Results: Total fat oxidation rates increased by 24.9 % from 0.241±0.025 to 0.301±0.009 g·min-1 with dGTE (P=0.05; ηp2 = 0.45) by week 4, whereas substrate utilisation was unaltered with PL. Body fat significantly decreased with dGTE by 1.63±0.16 % in contrast to PL over the intervention period (P<0.001; ηp2 = 0.84). No significant changes for FFA or blood pressure between groups were observed. dGTE resulted in a 10.9 % improvement in performance distance covered from 20.23±0.54 km to 22.43 ± 0.40 km by week 4 (P<0.001; ηp2 = 0.85). Conclusions: A 4 week dGTE intervention favourably enhanced substrate utilisation and subsequent performance indices, but did not alter TFA concentrations in comparison to PL. The results support the use of catechin polyphenols from dGTE in combination with exercise training in recreationally active volunteers

Assessing a commercially available sports drink on exogenous carbohydrate oxidation, fluid delivery and sustained exercise performance

Background: Whilst exogenous carbohydrate oxidation (CHOEXO) is influenced by mono- and disaccharide combinations, debate exists whether such beverages enhance fluid delivery and exercise performance. Therefore, this study aimed to ascertain CHOEXO, fluid delivery and performance times of a commercially available maltodextrin/ fructose beverage in comparison to an isocaloric maltodextrin beverage and placebo. Methods: Fourteen club level cyclists (age: 31.79 ± 10.02 years; height: 1.79 ± 0.06 m; weight: 73.69 ± 9.24 kg; VO2max: 60.38 ± 9.36 mL · kg·-1 min−1) performed three trials involving 2.5 hours continuous exercise at 50% maximum power output (Wmax: 176.71 ± 25.92 W) followed by a 60 km cycling performance test. Throughout each trial, athletes were randomly assigned, in a double-blind manner, either: (1) 1.1 g · min−1 maltodextrin + 0.6 g · min−1 fructose (MD + F), (2) 1.7 g · min−1 of maltodextrin (MD) or (3) flavoured water (P). In addition, the test beverage at 60 minutes contained 5.0 g of deuterium oxide (2H2O) to assess quantification of fluid delivery. Expired air samples were analysed for CHOEXO according to the 13C/12C ratio method using gas chromatography continuous flow isotope ratio mass spectrometry. Results: Peak CHOEXO was significantly greater in the final 30 minutes of submaximal exercise with MD + F and MD compared to P (1.45 ± 0.09 g · min−1, 1.07 ± 0.03 g · min−1and 0.00 ± 0.01 g · min−1 respectively, P < 0.0001), and significantly greater for MD + F compared to MD (P = 0.005). The overall appearance of 2H2O in plasma was significantly greater in both P and MD + F compared to MD (100.27 ± 3.57 ppm, 92.57 ± 2.94 ppm and 78.18 ± 4.07 ppm respectively, P < 0.003). There was no significant difference in fluid delivery between P and MD + F (P = 0.078). Performance times significantly improved with MD + F compared with both MD (by 7 min 22 s ± 1 min 56 s, or 7.2%) and P (by 6 min 35 s ± 2 min 33 s, or 6.5%, P < 0.05) over 60 km. Conclusions: A commercially available maltodextrin-fructose beverage improves CHOEXO and fluid delivery, which may benefit individuals during sustained moderate intensity exercise. The greater CHOEXO observed when consuming a maltodextrin-fructose beverage may support improved performance times

An Acute Increase of Dietary Protein Intake Elicits Positive Cellular Metabolic Adaptations in Healthy Males

There is emerging literature demonstrating that restricting dietary carbohydrate (CHO) intake might upregulate cellular markers of mitochondrial biogenesis. Mitochondria quantity and density has been linked with increased endurance performance, reduction in type 2 diabetes and improved insulin sensitivity. A number of transcriptional cellular markers have been identified as key regulators of this process. PURPOSE: To determine the influence of 7 days dietary manipulation on resting metabolic rate (RMR), body composition and transcriptional markers of mitochondrial biogenesis. METHOD: Forty-six healthy male participants (mean ± SD; age (years), body mass (kg), height (cm); 28 ± 5, 75.6 ± 11.1, 178.0 ± 4.9, respectively) were recruited and randomised to one of four conditions: energy matched high protein (PRO-EM), energy restricted high protein (PRO-ER), energy matched high carbohydrate (CHO-EM) or energy restricted high carbohydrate (CHO-ER). Macronutrient ratios (PRO:CHO:FAT) of 40:30:30 and 60:10:30 were used for high protein and high carbohydrate conditions, respectively. Calorific intake for energy restricted groups was matched to RMR. Participants visited the laboratory on 3 occasions across 15 days. On days 0, 7 and 15 participants completed assessments of body composition (DEXA) and RMR (indirect calorimetry), prior to providing a muscle biopsy from the vastus lateralis for later analysis of transcriptional markers via real-time polymerase chain reaction. Between days 1 & 7 and 7 & 14 participants consumed their habitual and prescribed diets, respectively. Laboratory testing was completed following an overnight fast and at the same time of day on each occasion. RESULTS: No difference in RMR was observed in any group across all time points. AMPK, PGC-1a, SIRT1 and PPAR expression was increased in the PRO-ER group (1.32, 1.20, 1.45 and 1.41 fold, respectively). Transcriptional markers were not affected in either CHO group. The CHO-ER group demonstrated a greater loss in lean mass relative to the PRO-EM (-2.22 vs -0.35%,) and body mass loss relative to both CHO-EM and PRO-EM (-2.85 vs -0.95 vs -1.47%) (P < 0.05). CONCLUSION: A restriction energy intake combined with increased protein consumption for 7 days increases transcriptional markers of mitochondrial biogenesis

Full-field Strain Methods for Investigating Failure Mechanisms in Triaxial Braided Composites

Composite materials made with triaxial braid architecture and large tow size carbon fibers are beginning to be used in many applications, including composite aircraft and engine structures. Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape. Although the large unit cell size of these materials is an advantage for manufacturing efficiency, the fiber architecture presents some challenges for materials characterization, design, and analysis. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A potential problem with using standard tests methods for these materials is that the unit cell size can be an unacceptably large fraction of the specimen dimensions. More detailed investigation of deformation and failure processes in large unit cell size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. In recent years, commercial equipment has become available that enables digital image correlation to be used on a more routine basis for investigation of full field 3D deformation in materials and structures. In this paper, some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques are presented. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12 and 24 k yarns and a 0/+60/-60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed, and this local failure had a significant effect on global stiffness and strength. The matrix material had a large effect on local damage initiation for the two matrix materials used in this investigation. Premature failure in regions of the unit cell near the edge of the straight-sided specimens was observed for transverse tensile tests in which the braid axial fibers were perpendicular to the specimen axis and the bias fibers terminated on the cut edges in the specimen gage section. This edge effect is one factor that could contribute to a measured strength that is lower than the actual material strength in a structure without edge effects

Characterization of Damage in Triaxial Braid Composites Under Tensile Loading

Carbon fiber composites utilizing flattened, large tow yarns in woven or braided forms are being used in many aerospace applications. Their complex fiber architecture and large unit cell size present challenges in both understanding deformation processes and measuring reliable material properties. This report examines composites made using flattened 12k and 24k standard modulus carbon fiber yarns in a 0 /+60 /-60 triaxial braid architecture. Standard straight-sided tensile coupons are tested with the 0 axial braid fibers either parallel with or perpendicular to the applied tensile load (axial or transverse tensile test, respectively). Nonuniform surface strain resulting from the triaxial braid architecture is examined using photogrammetry. Local regions of high strain concentration are examined to identify where failure initiates and to determine the local strain at the time of initiation. Splitting within fiber bundles is the first failure mode observed at low to intermediate strains. For axial tensile tests splitting is primarily in the 60 bias fibers, which were oriented 60 to the applied load. At higher strains, out-of-plane deformation associated with localized delamination between fiber bundles or damage within fiber bundles is observed. For transverse tensile tests, the splitting is primarily in the 0 axial fibers, which were oriented transverse to the applied load. The initiation and accumulation of local damage causes the global transverse stress-strain curves to become nonlinear and causes failure to occur at a reduced ultimate strain. Extensive delamination at the specimen edges is also observed

A valid and reliable nutrition knowledge questionnaire for track and field athletes

Background: Establishing an understanding of an athlete’s nutrition knowledge can inform the coach/practitioner and support the development of the athlete. Thus the purpose of the study was to develop a psychometrically valid and reliable tool to assess general and sport nutrition knowledge. Methods: An 85 question questionnaire was developed in consultation with a panel of experts. Ninety-eight participants from the UK completed the questionnaire, and again 3 weeks later. The participants were classified into two groups:those with nutrition (NUT, n= 53) training (sport nutritionists and dietitians who were either practicing or undertaking a postgraduate qualification in the field), and those without (NONUT,n= 48) training (professionals and postgraduate students with no exposure to any form of nutrition training). The questionnaire was then administered to a pilot cohort of UK based track and field athletes (n= 59) who were requested to time how long it took to complete the questionnaire. Results: Psychometric statistical analysis of the results was completed, resulting in the removal of 23 questions for a total of 62 questions in the final questionnaire. The validated questionnaire was then administered to 58 track and field athletes. Internal consistency was assessed using Chronbach’salpha(α>0.7),Pearson’scorrelation(p< 0.05) was used to assess reliability. Construct validity was evaluated using at-test (p< 0.05). A total test retest correlation of 0.95 was achieved (sub-section range: 0.87–0.97). Internal consistency was accepted in each sub-section (α=0.78–0.92) and the nutrition-trained group scored significantly higher on the overall questionnaire (80.4 vs 49.6%). The overall score for the athletic group was 61.0%. Conclusion: The questionnaire satisfied all psychometric measures and provides a new valid and reliable tool to assess general and sport nutrition knowledge of track and field athlete